1. Field of the Invention
The present invention generally relates to semiconductor processing technologies and, more particularly, to a semiconductor wafer processing system.
2. Description of the Related Art
In the semiconductor industry, various processes can be used to deposit and etch materials on the wafers. These processes include material removal processes, such as chemical mechanical polishing (CMP), and deposition processes, such as electro chemical deposition (ECD).
Other material removal and deposition processes have more recently been introduced. These include electrochemical mechanical processing (ECMPR) including electrochemical mechanical deposition (ECMD) and electrochemical mechanical etching (ECME), which are described in U.S. Pat. No. 6,176,992 entitled xe2x80x9cMethod and Apparatus For Electro Chemical Mechanical Depositionxe2x80x9d, commonly owned by the assignee of the present invention.
In the ECMD process, a conductor such as copper may be deposited on a semiconductor wafer or a work piece by having electrical current carried through an electrolyte that comes into contact with the surface of the wafer (cathode). The ECMD process, in one aspect, is able to uniformly fill the holes and trenches on the surface of the wafer with the conductive material while maintaining the planarity of the surface.
In the ECME process, a conductor such as copper previously deposited on a semiconductor wafer or a work piece can be removed by having electrical current carried through an electrolyte that comes into contact with the surface of the wafer (anode). The ECME process, in one aspect, is able to uniformly remove the conductor in a planar manner, thus maintaining the planarity of the surface.
A more detailed description of the ECMPR methods and apparatus can be found in the U.S. Pat. No. 6,176,992, noted above.
As generally exemplified in FIG. 1, the ECMPR system 10, being used for ECMD, includes a deposition chamber 12 which contains an anode 14, a pad 16 having openings 18 and an electrolyte 20 filling the chamber 12. The anode 14 may be attached to the bottom of the chamber 12. Further, a carrier head 22 having a rotatable shaft 23 holds and positions the wafer 24 against the pad 16. The wafer 24 is placed on a surface 26 of a carrier base 28 (chuck) of the carrier head 22. During the deposition and mechanical material removal steps, the carrier head secures 22 the wafer 24 to the surface 26 of the base 28 of the carrier head 22 by applying vacuum to the back of the wafer and using clamps 30. Vacuum is applied using vacuum lines 32 extending through the carrier base 28 and the body of the carrier head 22. Clamps 30 may also seal the electrical contacts to the wafer 24. During the material removal step, the carrier head provides a controllable load to the wafer to push it against the pad. A more detailed description of the carrier head may be found in the co-pending U.S. application Ser. No. 09/472,523, entitled xe2x80x9cWork Piece Carrier Head For Plating and Polishingxe2x80x9d filed Dec. 27, 1999, commonly owned by the assignee of the present invention. For a detailed description of the pad, reference can be made to assignee""s co-pending application Ser. No. 09/511,278, entitled xe2x80x9cPad Design and Structures For a Versatile Materials Processing Apparatusxe2x80x9d filed Feb. 23, 2000, the specification of which is incorporated by reference herein as non-essential matter.
During an ECMPR, the wafer carrier holds the wafer with proper vacuum suction. As a result, the wafer does not become detached by the application of a weak vacuum. Further, it is important that the wafer not become damaged by the application of a high vacuum suction. During ECMPR, back side of the wafer should not be exposed to the processing solutions, which could be a plating electrolyte. Also, in conventional CMP processes, during the process the wafer is held by a retaining ring that is placed around the circumference of the carrier head. Such systems allow process solutions, such as slurry, to wet the back side of the wafer during the CMP process. Conventional CMP systems do not use vacuum suction during the CMP process to hold the wafer on the carrier. Therefore there is a need in the industry for ECMPR or CMP systems that do not expose back side of the wafer to the processing solutions such as electrolyte or slurries.
Also, in such processes, a resilient cushion on which the backside of the wafer can rest should be provided. Methods and apparatus providing fall face contact for processing on the front face of the wafer while providing the above considerations are desirable in the industry.
To this end, there is a need for alternative carrier head designs.
It is an object of the present invention, therefore, to provide an improved carrier head.
It is a further object of the present invention to provide an improved carrier head that is usable for either electrochemical mechanical processing and chemical mechanical processing.
It is a further object of the present invention to provide a carrier head that does not expose the back of a wafer to processing solution, provides full face contact for processing on the front face of the wafer, and provides a resilient cushion on which the backside of the wafer can rest.
These and other objects of the invention, either singly or in combination, are achieved by the present invention. Most generally, the present invention uses some type of inflatable membrane during processing to establish a vacuum and/or provide a resilient cushion on which the backside of the wafer can rest.
In one aspect, the present invention provides an outer vacuum that allow for attachment of the wafer to the carrier head during processing, and also provides an inner inflatable membrane that provides a resilient cushion on which the backside of the wafer can rest during processing.
In other aspects, the present invention provides a membrane that is displaceable with a vacuum within certain cavity regions to provide for attachment of the wafer to the wafer carrier.